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kimg supports two categories of transforms: non-destructive per-layer transforms that preserve the original pixel data, and destructive operations that permanently modify the buffer.

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Non-destructive transforms

Image, paint, and shape layers support non-destructive transforms. These transforms are applied at render time without modifying the source pixel data.

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Position

Move a layer by setting its x and y coordinates: 
doc.setLayerPosition(layerId, 10, 20);

// or
doc.updateLayer(layerId, { x: 10, y: 20 });

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Rotation

Rotate a layer by an arbitrary angle (in degrees, clockwise): 
doc.updateLayer(layerId, {
  rotation: 30,
});

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Scale

Scale a layer horizontally and vertically: 
doc.updateLayer(layerId, {
  scaleX: 1.25,
  scaleY: 0.75,
});

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Flip

Flip a layer along the X or Y axis: 
doc.updateLayer(layerId, {
  flipX: false,
  flipY: true,
});

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Anchor points

The anchor determines the origin point for transforms. Two options are available:
  • topLeft (default): Transforms are applied relative to the top-left corner
  • center: Transforms are applied relative to the center of the layer
doc.updateLayer(layerId, {
  anchor: 'center',
  rotation: 45,
});

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Combined example

All transform properties can be set together: 
doc.updateLayer(layerId, {
  x: 10,
  y: -4,
  anchor: "center",
  flipX: false,
  flipY: true,
  rotation: 30,
  scaleX: 1.25,
  scaleY: 0.75,
});

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Destructive transforms

These operations permanently modify the layer’s pixel buffer.

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Resize

Resize a layer using one of three algorithms:

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Nearest-neighbor

Fast and lossless for pixel art: 
doc.resizeLayerNearest(layerId, 256, 256);

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Bilinear

Smooth interpolation for photos: 
doc.resizeLayerBilinear(layerId, 512, 512);

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Lanczos3

Highest quality for photo downscaling (slower): 
doc.resizeLayerLanczos3(layerId, 128, 128);

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Crop

Extract a rectangular sub-region: 
doc.cropLayer(layerId, {
  x: 16,
  y: 16,
  width: 64,
  height: 64,
});

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Trim

Auto-crop to the bounding box of non-transparent pixels: 
doc.trimLayerAlpha(layerId);

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Rotate (destructive)

Rotate by an arbitrary angle with bilinear interpolation. The output buffer is sized to contain the full rotated image: 
doc.rotateLayer(layerId, 45.5);
For 90-degree-increment rotations, prefer the non-destructive rotation property which is lossless and faster.

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Transform performance

Non-destructive transforms are cached at render time. If you apply the same transform multiple times, only the first render will compute the transformed raster. Subsequent renders reuse the cached result until the source buffer or transform properties change. See ~/workspace/source/crates/kimg-core/src/transform.rs:1-18 for resize algorithm details and ~/workspace/source/crates/kimg-core/src/layer.rs:132-168 for the transform cache implementation.

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